The best Xbox 360 shooter for me has been Call of Duty 2. It may not be the best graphical game out there, but it is for me the best over all. With the four play split screen or the eight players on-line before they cut those servers. Even if your not into all that, but want to play single player it does have good and bad sides to it. Of course there will be those damn random grenades coming at you, but then again what Call of Duty Series doesn't have it. 

The price and over all approach of this game for me is the best one for me. When I did play this I played with a group of guys were we played customized matches and it is the one thing that it did better then all others. This game showed why private matches need to be in the shooter genre. The voice chat was decent in this game as well. In this case less is more when it comes to shooters. 

Who really needs all those features or commands that you won't use. Simplicity is where this game shines even though it may be dated. Oh for you achievement people this game would be good as it all comes from single player. To gain them all it will take about eight to ten hours to gain them all. It is about one of the only games that I believe to have true achievements.